Transmission method, sending device and receiving device

ABSTRACT

Stream data and a command output from a drive device are individually packetized in a first packet processing unit. The stream data packet and the command packet are further multiplexed, and the multiplexed data is transmitted to a transmission path using a synchronous channel. When the command output from a decoding unit is packetized in a second packet processing unit, it is packetized by multiplexing flow control information output from the decoding unit, and is transmitted to the first packet processing unit using a synchronous channel of the transmission path. Based on this flow control information, reading/writing by the drive device is controlled.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmission method of digital datatypified by DVD-Video and others, and particularly to a transmissionmethod of stream data or a command outputted from a stream data sendingdevice, and a command or flow control information outputted from astream data receiving device.

2. Description of the Related Art

There is a conventional method for transmitting data recorded on a CD(compact disk) or the like, called MOST (Media-Oriented SynchronousTransfer), for example. (References: Patric Heck, et al.: “MediaOriented Synchronous Transfer—A Network Protocol for High-Quality,Low-Cost transfer of Synchronous, Asynchronous, and Control Data onFiber Optic”, Presented at AES103rd Convention, 1997 September, Preprint4551, or www.rnostcooperation.com)

The conventional data transmission method according to the MOST methodwill be explained below with reference to FIG. 1.

FIG. 1 is a diagram that shows a data structure of a frame in the MOSTmethod.

According to the conventional transmission method, data is transmittedin a frame transmitted at 44.1 kHz, that is, every 22.67 microseconds. Adata length of one frame is 512 bits. As shown in FIG. 1, one frameconsists of a preamble 701, a boundary descriptor 702, a synchronouschannel area 703, an asynchronous channel area 704, a control frame 705,a frame control data 706 and a parity 707. The frame cycle is notlimited to 44.1 kHz, but may be 48 kHz. In the following explanation,the frame cycle is 44.1 kHz, for convenience.

Here, the preamble 701, the boundary descriptor 702, the synchronouschannel area 703 in the frame will be explained, but the explanation ofthe asynchronous channel area 704, the control frame 705, the framecontrol data 706 and the parity 707 will be omitted because they are notdirectly related to the present invention.

The preamble 701 is data of 4 bits having a fixed pattern, and used fordetecting a boundary of a frame in a sending device and a receivingdevice that transmit the data. The boundary descriptor 702 is data of 4bits and is used for indicating the boundary between the synchronouschannel area 703 and the asynchronous channel area 704.

The synchronous channel area 703 is data of 0˜480 bits long, and itslength is determined by the boundary descriptor 702. The synchronouschannel area 703 is used for transmission of real time data such asvoice data. Here, the real time data means the data with timeconstraints, and in transmission of that data, the transmission delaymust be definable.

The synchronous channel area 703 is assigned to the sending device andthe receiving device as a time slot. Up to 60 time slots can be used asa synchronous channel. The time slots used for transmission are assignedto the sending device and the receiving device in advance, and a groupof time slots used for one transmission is defined as a logical channel.The sending device sends data using the assigned time slot, and thereceiving device receives the data using the assigned time slot. In theMOST method, data transmission using one time slot corresponds to thedata transmission at a speed of 352.8 kbps. In other words, five timeslots are used in the synchronous channel area 703 in order to transmitdata of a CD at a speed of 1.6122 Mbps.

A command or the response thereto is usually transmitted using thecontrol frame 705.

In the conventional transmission method, the stream data is transmittedusing the synchronous channel area 703, and the command is transmittedusing the control frame 705. As for DVD (digital versatile disk)-Video,the disk includes compressed data under the standard of MPEG-2. Sincethe speed of reading out data by the drive device is generally higherthan that of decoding the data by the decoding unit, flow control occursin the drive device. Therefore, when the data of DVD-Video istransmitted via a network, the information on this flow control(hereinafter referred to as “flow control information”) also needs to betransmitted.

However, the method for transmitting the flow control information is notdetermined in the MOST method, so the above flow control cannot beexecuted appropriately.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is designed in view of the above problem, and theobject of the present invention is to provide a transmission method thatenables execution of flow control when the method of transmitting theflow control information is not determined (particularly in the MOSTmethod). In addition, another object of the present invention is toprovide a transmission method that enables use of a transmissionbandwidth efficiently.

In order to achieve the above objects, the transmission method accordingto the present invention is a transmission method of transmitting streamdata from a sending device to a receiving device using a digitaltransmission path having a first channel and a second channel,including: a first step for sending stream data from the sending deviceto the receiving device using the first channel; and a second step forsending, from the receiving device to the sending device using thesecond channel, a command including flow control information indicatingan instruction to have the sending device start or stop sending of thestream data, wherein the second channel is a synchronous channel thatcan guarantee to send data within a certain time period of atransmission delay.

Accordingly, the flow control information is transmitted from thereceiving device to the sending device by a synchronous channel, so theflow control information is transmitted to the sending device withoutfail and thereby the stream data can be transmitted stably.

Also, in order to achieve the above objects, the command according tothe present invention has a header part including a synchronous code anda data part indicating a command, and in the second step, the flowcontrol information is placed on the header part of the command.

Accordingly, the flow control information can be transmitted from thereceiving device to the sending device by being multiplexed on theheader of the packet, so there is an effect that the bandwidth of thedigital transmission path can be used efficiently. Also, since the flowcontrol information can be transmitted by being multiplexed on theheader of the packet, there is an effect that the data can betransmitted to the drive device pursuant to ATA or ATAPI which is asimilar transmission method.

Furthermore, in order to achieve the above objects, the transmissionmethod according to the present invention further includes a third stepof sending the command from the sending device to the receiving device,wherein the command sent in the third step has a header part including asynchronous code and a data part indicating a command.

Accordingly, the command can be sent from the sending device to thereceiving device, so the data can be transmitted from the sending deviceto the receiving device by interruption and thereby the stream data canbe transmitted more flexibly.

Also, in order to achieve the above objects, the sending deviceaccording to the present invention is a sending device that sends streamdata to a receiving device using a digital transmission path having afirst channel and a second channel, comprising: a buffer unit operableto temporarily hold stream data to be sent; a stream data sending unitoperable to read the stream data from the buffer unit, and send thestream data to the receiving device using the first channel; and acontrol unit operable to receive flow control information sent from thereceiving device using the second channel, and start or stop anoperation of the stream data sending unit based on the received flowcontrol information, wherein the second channel is a synchronous channelthat can guarantee to send data within a certain time period of atransmission delay.

Accordingly, the sending device controls sending of the stream databased on the flow control information sent from the receiving device.Thus, the data can be transmitted using the bandwidth of thetransmission path efficiently.

In addition, in order to achieve the above objects, the receiving deviceaccording to the present invention is a receiving device that receivesstream data sent from a sending device using a digital transmission pathhaving a first channel and a second channel, comprising: a receivingunit operable to receive stream data sent from the sending device usingthe first channel; a buffer unit operable to temporarily hold thereceived stream data; and a sending unit operable to send, to thesending device using the second channel, a command including flowcontrol information indicating an instruction to have the sending devicestart or stop sending of the stream data, based on amount of the streamdata stored in the buffer unit, wherein the second channel is asynchronous channel that can guarantee to send data within a certaintime period of a transmission delay.

Accordingly, the receiving device sends the flow control information tothe sending device depending upon its own receiving capability andcontrols sending of the stream data based on the flow controlinformation, so the data can be transmitted using the bandwidth of thetransmission path efficiently.

Note that, in order to achieve the above objects, the present inventioncan be realized as a program having a computer execute all thecharacteristic steps of the transmission method. And the program cannotonly be stored in a ROM and others of the transmission device, but alsodistributed via a recording medium such as a CD-ROM and a transmissionmedium such as a communication network.

BRIEF DESCRIPTION OF DRAWINGS

These and other subjects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the invention. In the Drawings:

FIG. 1 is a diagram that shows a data structure of a frame in the MOSTmethod.

FIG. 2 is a diagram that shows an example of the transmission deviceaccording to the present embodiment.

FIG. 3 is a diagram for explaining the transmission method according tothe present embodiment.

FIG. 4 is an example of a command packet format according to the presentembodiment.

FIG. 5 is a diagram that shows an actual example of control signalinformation of the command packet according to the present embodiment.

FIG. 6 is a diagram that shows a structure example of a first packetprocessing unit according to the present embodiment.

FIG. 7 is a diagram that shows a state transition of a stream data I/Funit of the first packet processing unit in FIG. 6.

FIG. 8 is a diagram that shows a state transition of a memory I/F unitof the first packet processing unit in FIG. 6.

FIG. 9 is a diagram that shows a structure example of a second packetprocessing unit according to the present embodiment.

FIG. 10 is a structure example of an ATAPI command packet according tothe present embodiment.

FIG. 11 is a structure example of a NULL packet which is one of thecommand packets according to the present embodiment.

FIG. 12A is a structure example of a register packet according to thepresent embodiment.

FIG. 12B is a diagram for explaining a data structure of the registerpacket in FIG. 12A.

FIG. 13 is a structure example of a status packet according to thepresent embodiment.

FIG. 14 is a diagram for explaining a stream data packet according tothe present embodiment.

FIG. 15 is a structure example of a NULL packet which is one of thestream data packets according to the present embodiment.

FIG. 16A is a diagram for explaining operations performed when a valueof an ATA register is read out according to the present embodiment.

FIG. 16B is a diagram for explaining operations performed when the valueof the ATA register is written in according to the present embodiment.

FIG. 17 is a diagram for explaining operations performed when an ATAPIcommand is sent according to the present embodiment.

FIG. 18 is a sequence diagram that shows operations performed when thedata is read out from the drive device according to the presentembodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed explanation of the transmission deviceaccording to the embodiment of the present invention with reference tothe figures.

FIG. 2 is a diagram that shows an example of the transmission device 10according to the present embodiment. As shown in FIG. 2, thetransmission device 10 includes a sending device 11, a receiving device12, a transmission path 104 connecting the sending device 11 and thereceiving device 12, and a display device 106.

The sending device 11 has a drive device 101, a first packet processingunit 102 a, and a first transmission path I/F unit 103 a.

The drive device 101 reads data from a disk such as a DVD medium.

The first packet processing unit 102 a packetizes the stream data readby the drive device 101 or the command outputted from the drive device101, or receives the packet transmitted via the transmission path 104and outputs it to the drive device 101 as a command. Here, the streamdata means all kinds of data such as videos and sounds recorded on arecording medium, etc. These data is read out and outputted from thedrive device 101 as stream data.

The first transmission path I/F unit 103 a outputs the packet generatedin the first packet processing unit 102 a to the transmission path 104in accordance with the interface of the transmission path 104, orfetches the packet from the frame in accordance with the interface ofthe transmission path 104 and outputs it to the first packet processingunit 102 a.

The receiving device 12 has a decoding unit 105, a second packetprocessing unit 102 b and a second transmission path I/F unit 103 b.

The decoding unit 105 decodes data compressed by a compression meanssuch as MPEG-2 recorded on a DVD medium or the like.

The second packet processing unit 102 b packetizes the command outputtedfrom the decoding unit 105, or receives the packet transmitted via thetransmission path 104 and recognizes it, and outputs it to the decodingunit 105 as stream data or a command.

The second transmission path I/F unit 103 b outputs the packet generatedin the second packet processing unit 102 b to the transmission path 104in accordance with the interface of the transmission path 104, andfurther fetches the packet from the frame in accordance with theinterface of the transmission path 104 and outputs it to the secondpacket processing unit 102 b.

The drive device 101 includes a register 108 a such as an ATA register(the present embodiment will be explained on the assumption that theregister 108 a is an ATA register). The decoding unit 105 includes aregister 108 b that can hold the contents of the register 108 a of thedrive device 101. Furthermore, the first packet processing unit 102 aand the second packet processing unit 102 b respectively include abuffer 107 a and a buffer 107 b of several dozen k bytes˜several hundredk bytes, for instance, used for sending and receiving data of DVD or thelike. The size of the buffer 107 a, 107 b is not to be limited to theabove size. The first packet processing unit 102 a and the second packetprocessing unit 102 b respectively determine whether the data stored inthe buffer 107 a and the buffer 107 b has reached a predetermined valuea or more, or a predetermined value b or less.

The transmission path 104 connecting the sending device 11 and thereceiving device 12 has at least a synchronous channel area fortransmitting digital data. The transmission path 104 in the presentembodiment is a transmission path pursuant to the standard of the MOSTmethod having the synchronous channel area and the asynchronous channelarea as described above. (The transmission path 104 is not limited tothat in the MOST method, but may be an arbitrary transmission pathhaving a synchronous channel such as IEEE1394 or USB, for which acertain standard of a transmission bandwidth or delay can be defined).The packet generated in the first packet processing unit 102 a or thesecond packet processing unit 102 b is transmitted using the synchronouschannel area 703 of the transmission path 104.

The display device 106 receives the data decoded by the decoding unit105 and displays it, and is constructed using an arbitrary displaymethod such as CRT, liquid crystal or plasma.

Furthermore, the decoding unit 105 controls the drive device 101 via thetransmission path 104 according to a command. For example, by sending acommand “Read” (as an example of a command for requesting stream data)from the decoding unit 105, the drive device 101, upon receiving thiscommand, reads the stream data from a DVD-Video medium and has thedecoding unit 105 send it.

Here, the decoding unit 105 controls the drive device 101 using an ATAPIcommand as a command for controlling the drive device 101. As for theinterface between the drive device 101 and the first packet processingunit 102 a and the interface between the decoding unit 105 and thesecond packet processing unit 102 b, the stream data and the command aredescribed separately. The ATAPI command is transmitted by theseinterfaces. Or they may be the interfaces like ATA by which themultiplexed stream data and command are sent via the same bus. In thiscase, the first packet processing unit 102 a and the second packetprocessing unit 102 b perform separation between the stream data and thecommand, multiplexing of them or interface processing of them. ATAPI andATA are standards. ATAPI and ATA are standardized as (T13D 1321D ATAttachment with Packet Interface 5), and the DVD control command underthe ATAPI is standardized as (SFF Committee Information Specificationfor ATAPI DVD Device Rev 4.0 Feb. 10, 2000).

Next, transmission of a command packet and a stream data packet will beexplained using FIG. 3. Here, the command packet means a packetincluding the command which is packetized in the first packet processingunit 102 a or the second packet processing unit 102 b. The stream datapacket means a packet including the stream data which is packetized inthe first packet processing unit 102 a or the second packet processingunit 102 b.

As shown in FIG. 3, the command packet and the stream data packet aretransmitted via different synchronous channels. For example, thereceiving device 12 sends the command packet to the sending device 11using the second synchronous channel 21. The sending device 11 sends thecommand packet to the receiving device 12 using the third synchronouschannel 22. And the sending device 11 sends the stream data packet tothe receiving device 12 using the first synchronous channel 20.

The synchronous channel 21 and the synchronous channel 22 for sendingthe command packet require the bandwidth of approximately several tensof kbps˜several hundred kbps. The synchronous channel 20 for sending thestream data packet requires the bandwidth of 11.08 Mbps or more for DVD.The bandwidth is not to be limited to the above bandwidth, and it may bespecified for each type of media. Also, the synchronous channel 22 andthe synchronous channel 20 may be integrated into one channel and themultiplexed command packet and stream data packet may be sent via thechannel. However, in the following explanation, they are sentseparately, if there is no specific description.

Next, an example of a command packet format used in the presentembodiment is shown in FIG. 4. This packet consists of a header 201 anda data part 202. The header 201 consists of an SYNC part 203 and acontrol data part 206. In the SYNC part 203, codes for synchronizingtransmission of packets are stored. The control data part 206 consistsof a packet type indicating a packet type and control signal information(C0˜C4) required for the operations of the driver and the decoder. Thiscontrol signal information is an example of the flow control informationaccording to the present invention, and is used for controlling the datatransmission flow requiring immediacy. At least the flow controlinformation of DVD-Video is transmitted using this control data part206.

FIG. 5 is a diagram that shows an actual example of the above controlsignal information. Here, C0 is transmitted from the receiving device 12to the sending device 11 as a reset instruction of the drive device 101.C0 is also transmitted from the sending device 11 to the receivingdevice 12 as an interrupt signal (a notice which is given when anoperator of the drive device 101 makes an operation entry, forinstance).

C1 is a flow control signal, and used when the receiving device 12instructs the sending device 11 to send and stop sending data. Forexample, it is predetermined that “H” and “L” indicate “Wait” and“Ready” respectively, and the receiving device 12 gives the instructionbased on these. C1 is also used when the sending device 11 gives theinstruction to the receiving device 12. For example, since the streamdata is sent from the receiving device 12 to the sending device 11 ifthe drive device 101 of the sending device 11 is a recording device suchas a DVD-RAM or a DVD-R, C1 is used for the flow control in that case.Likewise, it is predetermined that “H” and “L” indicate “Busy” and“Ready” respectively, and the sending device 11 gives the instructionbased on these.

C3 is a signal used when a data error occurs in transferring data. Forexample, when an error occurs in reading out data and resending isrequested, C3 is used by setting at “H”.

C4 is a signal for instructing buffer clear, and used for instructing toclear the data held in the buffers 107 a, 107 b of the first and secondpacket processing units 102 a, 102 b. The allocation of these controlsignals is, of course, not limited to that of FIG. 5, and a part ofthese signals may be used for the control. Furthermore, an areacorresponding to a signal line for ATA that transmits a control signalfor DMA such as DMA Stop, DMA ACK or DMA Req, which are not shown inFIG. 5, may be set for exchanging the signal, and used for the control.

Next, a structure of the above-mentioned first packet processing unit102 a will be explained using FIGS. 6˜8. FIG. 6 is a diagram that showsa structure example of the first packet processing unit 102 a accordingto the present embodiment. FIG. 7 is a diagram that shows a statetransition of the stream data I/F unit 305 in the first packetprocessing unit 102 a. FIG. 8 is a diagram that shows a state transitionof the memory I/F unit 306 in the first packet processing unit 102 a.

In FIG. 6, the first packet processing unit 102 a includes a stream dataprocessing unit 301 that processes the stream data received from thedrive device 101, an output command processing unit 302 that processesthe command received from the drive device 101, an input commandprocessing unit 303 that processes the command transmitted from thedecoding unit 105 via the transmission path 104, and a multiplexing unit304 that multiplexes the stream data packet generated by the stream dataprocessing unit 301 and the command packet generated by the outputcommand processing unit 302.

First, the stream data processing unit 301 will be explained. The streamdata processing unit 301 includes a stream data I/F unit 305, a memoryI/F unit 306, a buffer 107 a and a stream data output unit 308.

The stream data I/F unit 305 receives the stream data outputted from thedrive device 101, and outputs it to the memory I/F unit 306. The streamdata I/F unit 305 receives the stream data according to the interface ofthe drive device 101. Also, the stream data I/F unit 305 receives theflow control signal from the memory I/F unit 306, and confirms whetheror not it is to receive the stream data based on the flow controlsignal. When this flow control signal is HS1 and HS1 is “0”, the streamdata I/F unit 305 receives the stream data, and when HS1 is “1”, itstops receiving the stream data. In summary, the stream data I/F unit305 does not receive the stream data from the drive device 101 when thesignal HS1 is “1”.

Here, an example of the state transition in the stream data I/F unit 305will be explained using FIG. 7. FIG. 7 shows three states to which thestream data I/F unit 305 can transition: a state 401 of waiting forreceiving stream data, a state 402 of receiving stream data and a state403 of outputting stream data to the memory I/F unit 306.

The stream data I/F unit 305 starts from the state 401 of waiting forreceiving stream data outputted from the drive device 101. In this state401, when the signal HS1 outputted from the memory I/F unit 306 is “0”,the stream data I/F unit 305 transitions to the state 402 of receivingthe stream data, and when the signal HS1 is “1”, it keeps the state 401.When the signal HS1 became “1” and the stream data I/F unit 305 receivedthe stream data from the drive device 101, but the stream data I/F unit305 has not received the stream data for the maximum value of the datapart 202 of the packet (255 bytes, for instance) in FIG. 4, ittransitions to the state 401 again.

On the other hand, when the stream data I/F unit 305 has received thestream data for the maximum value of the data part 202 of the packet, ittransitions to the state 403 of outputting the stream data to the memoryI/F unit 306. As for DVD, since the data is recorded by sector, a newpacket is generated when the boundary between the sectors is detected.The stream data I/F unit 305 also transitions to the state 403 in thiscase. And when the output of the stream data from the stream data I/Funit 305 to the memory I/F unit 306 has been completed, it transitionsto the state 401.

In this manner, the stream data I/F unit 305 executes the flow controlusing the flow control signal HS1. The memory I/F unit 306 outputs thepacketized data to the stream data output unit 308 while writing thestream data received from the stream data I/F unit 305 into the buffer107 a.

Also, the memory I/F unit 306 manages the data amount in the buffer 107a. When the free space of the buffer 107 a becomes a predetermined valueor less, the memory I/F unit 306 notifies the stream data I/F unit 305of that effect with a flow control signal. This flow control signalcorresponds to the above-mentioned HS1.

Furthermore, the memory I/F unit 306 receives the flow control signalfrom the command packet recognition unit 312, and determines whether ornot it is to receive the stream data based on the flow control signal.When this flow control signal is HS2 and HS2 is “0”, it receives thestream data, and when HS2 is “1”, it does not receive the stream data.In summary, when the signal HS2 is “1”, the memory I/F unit 306 outputsan empty packet without the data part 202 (NULL packet) to the streamdata output unit 308, and when the signal HS2 is “0”, it reads out thestream data from the buffer 107 a, packetizes it, outputs it to thestream data output unit 308.

Here, an example of the state transition of the memory I/F unit 306 willbe explained using FIG. 8. FIG. 8 shows three states to which the memoryI/F unit 306 can transition: a state 501 of outputting an empty packetto the stream data output unit 308, a state 502 of reading data from thebuffer 107 a, and a state 503 of outputting packet to the stream dataoutput unit 308.

The memory I/F unit 306 starts from the state 501 of outputting an emptypacket (NULL packet) to the stream data output unit 308. In this state501, when the signal HS2 is “1” or there is no data in the buffer 107 a,the memory I/F unit 306 keeps the state 501, and when the signal HS2 is“0” and there is data in the buffer 107 a, it transitions to the state502 of reading out the data from the buffer 107 a.

In the state 502, the memory I/F unit 306 reads out data from the buffer107 a, packetizes the read-out data, and transitions to the state 503 ofoutputting the packet to the stream data output unit 308.

In the state 503, the memory I/F unit 306 outputs the packet to thestream data output unit 308, and then transitions to the state 502 againwhen the signal HS2 is “0” and the there is data in the buffer 107 a. Onthe other hand, it transitions to the state 501 when the signal HS2 is“1” or there is no data in the buffer 107 a.

In this manner, the memory I/F unit 306 executes the flow control basedon the flow control signal and whether or not there is data in thebuffer 107 a.

After that, the stream data output unit 308 receives the packet from thememory I/F unit 306 and outputs it to the multiplexing unit 304.

Next, the output command processing unit 302 will be explained. Theoutput command processing unit 302 includes a command I/F unit 309 and acommand output unit 310.

The command I/F unit 309 receives the command outputted from the drivedevice 101, packetizes it, and outputs it to the command output unit310. It receives the command in accordance with the interface of thedrive device 101. The packet as shown in FIG. 4 is used in this case.Also, when the command I/F unit 309 has not received the command, itoutputs an empty packet (or “NULL packet”) to the command output unit310. The command output unit 310 receives the packet from the commandI/F unit 309, and outputs it to the multiplexing unit 304.

Next, the input command processing unit 303 will be explained. The inputcommand processing unit 303 includes a packet input unit 311 and acommand packet recognition unit 312.

The packet input unit 311 receives a packet from the first transmissionpath I/F unit 103 a, and outputs it to the command packet recognitionunit 312. The command packet recognition unit 312 receives the packetfrom the packet input unit 311, and judges whether or not the packetincludes data. When the packet includes data, it writes the data intothe buffer unit 313. The data written in the buffer 313 is outputted tothe drive device 101 in accordance with the interface of the drivedevice 101. Also, when the received packet includes a flow controlsignal, the command packet recognition unit 312 notifies the memory I/Funit 306 of the information of the flow control signal.

As described above, the packet outputted from the first packetprocessing unit 102 a is sent to the first transmission path I/F unit103 a, and the first transmission path I/F unit 103 a outputs that datato the transmission path 104.

In the case of MOST method, the first transmission path I/F unit 103 aallocates the above-mentioned packet to the synchronous channel area 703of the frame as shown in FIG. 1, and outputs it according to theallocation. A bandwidth of a fixed transmission speed is allocated tothe synchronous channel area 703. In this case, a bandwidth of at least11.08 Mbps is allocated, and the multiplexed stream data packet and thecommand packet are transmitted via the transmission path 104. When thereis no data to be transmitted, an empty packet (NULL packet) including nodata is transmitted.

In the MOST method, transmission is performed via the transmission path104 by frame as shown in FIG. 1. In the present embodiment, since thestream data and the command are respectively packetized and multiplexedinto the same frame by the first packet processing unit 102 a, asdescribed above, they can be transmitted in the synchronous channelarea. Since the flow control information is also multiplexed into thecommand packet, it can be transmitted in the synchronous channel area.

Upon receiving the packet from the transmission path 104, the secondtransmission path I/F unit 103 b outputs the packet to the second packetprocessing unit 102 b. The second transmission path I/F unit 103 b alsooutputs the packet received from the second packet processing unit 102 bto the transmission path 104 according to the interface thereof.

Here, the structure of the second packet processing unit 102 b will beexplained.

The second packet processing unit 102 b packetizes the command in thepacket format as shown in FIG. 4 and outputs it to the secondtransmission path I/F unit 103 b. The second packet processing unit 102b further receives the packet transmitted via the transmission path 104and outputs it to the decoding unit 105.

The second packet processing unit 102 b has a buffer, which can hold thereceived data. The packet which the second packet processing unit 102 breceives includes the stream data packet and the command packet.Therefore, the stream data packet is to be processed by the stream dataprocessing unit 301, and the command packet is to be processed by theinput command processing unit 303.

The second packet processing unit 102 b does not packetize the streamdata but packetizes the command only. Here, the command means a command,a parameter necessary for executing the command and others. Note thatthe above-mentioned packetizing of the command is performed in the samemanner as that performed in the first packet processing unit 102 a.

Furthermore, the second packet processing unit 102 b generates a flowcontrol signal indicating whether or not the data is to be receivedbased on free space of a buffer provided for storing the stream data. Inother words, when the free space of the buffer becomes a predeterminedvalue or less, the second packet processing unit 102 b notifies thefirst packet processing unit 102 a that receiving of the data is to bestopped. Also, when a packet format is same as that of FIG. 4, this flowcontrol information is multiplexed into the control data part 206.

In the following, the structure of the above-mentioned second packetprocessing unit 102 b will be explained. FIG. 9 is a diagram that showsa structure example of the second packet processing unit 102 b accordingto the present embodiment.

In FIG. 9, the second packet processing unit 102 b includes adistribution unit 601 that distributes the multiplexed packet receivedfrom the first packet processing unit 102 a, a stream data processingunit 602 that processes the stream data packet distributed by thedistribution unit 601, an output command processing unit 603 thatprocesses the command received from the decoding unit 105, and an inputcommand processing unit 604 that processes the command packetdistributed by the distribution unit 601.

First, the distribution unit 601 receives the packet from the secondtransmission I/F unit 103 b, and distributes the packet into the streamdata packet and the command packet. Then, the distribution unit 601outputs the stream data packet to the stream data processing unit 602,and the command packet to the input command processing unit 604.

Next, the stream data processing unit 602 will be explained. The streamdata processing unit 602 includes a stream data input unit 605, a memoryI/F unit 606, a buffer 107 b and a stream data I/F unit 608.

The stream data input unit 605 outputs the stream data packet receivedfrom the distribution unit 601 to the memory I/F unit 606, and thememory I/F unit 606 fetches the necessary information from the receivedpacket and writes it in the buffer 107 b. When the memory I/F unit 606receives the request from the stream data I/F unit 608, it reads out thedata from the buffer 107 b, and outputs the data to the stream data I/Funit 608.

Furthermore, the memory I/F unit 606 manages the data amount of thebuffer 107 b. When the free space of the buffer 107 b becomes apredetermined value or less, the memory I/F unit 606 notifies the firstprocessing unit 102 a of it using a flow control signal. This flowcontrol signal corresponds to the signal HS2 as mentioned above.Accordingly, the memory I/F unit 606 multiplexes this flow controlsignal into the command packet, and outputs it to the command I/F unit609.

As for the control of the buffer 107 b by the memory I/F unit 606, itdoes not output the stream data until a certain amount of the streamdata is accumulated in the buffer 107 b. Thereby, a special reproductionsuch as fast-forward can be realized. Also, as for the transmission ofthe stream data, since the buffer 107 b regulates the data amount to betransmitted even if the transmission speed is limited due to thebandwidth of the transmission path 104, it is possible to continue thecommunication within the limit of that speed.

Furthermore, the buffer 107 b clears the stored data in response to aclear instruction or a certain command outputted from the decoding unit105. The command outputted from the decoding unit 105 is detected by thecommand I/F unit 609 of the second packet processing unit 102 b andnotified to the memory I/F unit 606.

The stream data I/F unit 608 outputs the stream data received from thememory I/F unit 606 to the decoding unit 105 according to the interfaceof the decoding unit 105.

Next, the output command processing unit 603 will be explained.

The output command processing unit 603 includes a command I/F unit 609and a command output unit 610. Their basic operation is same as that ofthe output command processing unit 302 of the first packet processingunit 102 a, as shown in FIG. 6.

The command I/F unit 609 receives the command outputted from thedecoding unit 105, packetizes it and outputs it to the command outputunit 610. This receiving of the command is performed in consideration ofthe interface of the decoding unit 105. The format of the packetgenerated here is same as that as shown in FIG. 4. When the command I/Funit 609 does not receive the command from the decoding unit 105, itoutputs an empty packet (NULL packet) to the command output unit 610.

Also, the command I/F unit 609 receives the flow control signal HS2 fromthe memory I/F unit 606 of the stream data processing unit 602, asmentioned above. The command can be multiplexed if this signal HS2 iswritten into the control data part 206 of the packet header.

Furthermore, the command I/F unit 609 detects whether there is a commandof clearing the data stored in the buffer 107 b, as mentioned above.When the command I/F unit 609 detects such a command, it notifies thebuffer 107 b so as to clear the data in the buffer 107 b.

Then, the command output unit 610 receives the packet from the commandI/F unit 609, and outputs it to the second transmission path I/F unit103 b.

Next the input command processing unit 604 will be explained.

The input command processing unit 604 includes a packet input unit 611and a command packet recognition unit 612.

The packet input unit 611 receives the command packet from thedistribution unit 601, and outputs it to the command packet recognitionunit 612. The command packet recognition unit 612 judges whether or notthe packet received from the packet input unit 611 includes data, andwhen it judges that the data is included, writes the data in the bufferunit 613. The data written in the buffer unit 613 is outputted to thedecoding unit 105 according to the interface of the decoding unit 105.

The decoding unit 105 decodes the stream data sent from the drive device101 via the transmission path 104 according to MPEG-2 or the like. Thedecoded data is outputted to the display device 106. The display device106 makes a display based on the digital data received from the decodingunit 105. Note that the display device 106 corresponds to a displayscreen for the image data and a loudspeaker for the sound data.

Meanwhile, the decoding unit 105, upon receiving the data from the drivedevice 101, outputs the command and the flow control information to thedrive device 101 based on the decoding condition of the data. These datais packetized in the second packet processing unit 102 b, as mentionedabove, and outputted to the drive device 101 via the transmission path104. Here, the command means a command, a parameter in the command, andothers, and the transmission of the command requires a bandwidth ofseveral dozen kbps.

In the following, structure examples of the other command packets thanthat as shown in FIG. 4 will be explained in detail using FIGS. 10˜13.Each packet is identified with a value of a packet type in the controldata part 206 in FIG. 4.

FIG. 10 is a structure example of an ATAPI command packet that transmitsan ATAPI command. As shown in FIG. 10, ATAPI command of 12 bytes (ATAPICommand[0]˜ATAPI Command[11]) is transmitted using the data part 202 ofFIG. 4. Note that the structure of the ATAPI packet is not limited tothis, but it may be an arbitrary structure that enables to transmit theATAPI command of 12 bytes.

FIG. 11 is an example of a NULL packet. The NULL packet is transmittedwhen the ATAPI command is transmitted, the data of the register is reador written, or there is no need to notify of the status. By doing so,the command packet which bursts out can be transmitted via thesynchronous channel. Since the synchronous channel is secured in thepresent embodiment, this NULL packet is necessary.

FIG. 12A is a structure example of a register packet for writing in andreading out from a register. FIG. 12B is a diagram for explaining themeaning of each bit in FIG. 12A. In FIGS. 12A and 12B, “r” (in the caseof “H”, for instance) indicates a packet for reading out a registervalue, and “w” (in the case of “H”, for instance) indicates a packet forwriting it in the register. DA0˜DA2 and CS0, CS1 indicate addresses ofthe registers which are read out and written in. For example, when r,CS0, CS1, DA0˜DA2 are “H”, “H”, “L”, “H”, “H”, “H”, respectively,“reading out from a status register” is indicated.

The meaning and address of each register are described in thespecifications of ATA/ATAPI. According to these specifications, thevalue of the register 108 a or the register 108 b can be read andwritten. The structure of the register packet is not limited to thatshown in FIG. 12A, but it may be an arbitrary structure that enables totransmit whether a register is read from or written in, an address ofthe register which is written in or read from, and a value to be writtenin the register.

FIG. 13 is an example of a status packet for transmitting the status ofthe register 108 a of the drive device 101. ATAPI Status, ATAPI Error,ATAPI Interrupt Reason, ATAPI Byte Count respectively correspond toregisters specified by the ATA/ATAPI standards,00000000000000000000000000 and transmit the values of the respectiveregisters. This packet enables to recognize the status of the register108 a. The structure of the status packet is not limited to that shownin FIG. 13, but it can be realized by an arbitrary structure thatenables to transmit the value of each register. Or it may be a structurethat enables to transmit at least a part of the registers.

As for the ATAPI command packet shown in FIG. 10, the register packetshown in FIG. 12, and the status packet shown in FIG. 13, a packetindicating that the reception of them is completed may be returnedthereto. Accordingly, even when an error occurs in the transmission path104, they can be transmitted without fail. The structure of the packetindicating the completion of reception is arbitrary.

Furthermore, a structure of the stream data packet will be explainedusing FIG. 14 and FIG. 15.

FIG. 14 shows a structure of the stream data packet that transmits thesector data read out from the drive device 101. The data of 32 bytes ineach row indicates the data for one frame in the MOST method, and eachcolumn indicates a byte location in one frame in the MOST method. In thecase of DVD-Video, one sector length is 2048 bytes, and the data of 2048bytes with a header attached is transmitted as a packet. Here, thesector data is transmitted after being encrypted, and the packet isdivided into an area not to be encrypted 801 and an area to be encrypted802. In the area not to be encrypted 801, “SYNC for encryption” forsynchronizing packets and “encryption control” indicating information ofwhether the packet is to be encrypted or not are transmitted. In thearea to be encrypted 802, a “header”, a “data length” and data aretransmitted. This header is same as that of the command packet asdescribed in FIG. 4. According to this structure, the stream data andthe command can be multi-transmitted. The command may be transmittedwithout being encrypted. Also, the header is unnecessary when thecommand is not multiplexed.

In order to transmit the stream data as shown in FIG. 14, 32 bytes aretransmitted in each frame in the MOST method. When the data of DVD-Videois transmitted, one stream data packet is transmitted using 65 frames ofthe MOST method. Therefore, the total bytes are 2080, and among them, 4bytes are not to be encrypted and the remaining 2076 bytes are to beencrypted. Among these 2076 bytes, 2 bytes are allocated to a header, 2bytes to a data length, 2048 bytes to data, and the remaining 24 bytesto an area for “Reserved”, which is padded with arbitrary data. The datalength to be transmitted can be changed by the data of the “data length”of 2 bytes, of course. For example, one sector data of 2064 bytes(including a header for the sector) may be transmitted. In this case, anarea for “Reserved” is 8 bytes long. The data of an arbitrary length canbe transmitted depending upon the data length. In that case, the numberof MOST frames and the length of the area for “Reserved” used fortransmitting one packet depend upon the data length.

FIG. 15 is a structure example of a NULL packet in the stream datapacket. The structure up to the header is same as that of theabove-mentioned stream data packet, but in the area following theheader, “Reserved” is padded. One NULL packet is transmitted in oneframe of the MOST method. Since there is no actual data in an area 902corresponding to the area 802 in FIG. 14, the area 902 does not need tobe encrypted.

FIGS. 16A and 16B are sequence diagrams that show how an ATA register isread from and written in. As shown in FIG. 16A, when the decoding unit105 instructs the second packet processing unit 102 b to read from theregister 108 a of the drive device 101, the second packet processingunit 102 b sets CS0, CS1, DA0˜DA2 and r and sends the register packet soas to instruct the address value and reading thereof. The first packetprocessing unit 102 a reads out from the register 108 a of the drivedevice 101 depending upon the contents of the received register packet,and sends the value to the second packet processing unit 102 b with theregister packet.

Also, as shown in FIG. 16B, when the decoding unit 105 instructs thesecond packet processing unit 102 b to write in the register 108 a ofthe drive device 101, the second packet processing unit 102 b sets CS0,CS1, DA0˜DA2 and w and sends the register packet so as to instruct theaddress value and writing thereof. The first packet processing unit 102a writes the value in the register 108 a of the drive device 101depending upon the contents of the received register packet.

FIG. 17 is a sequence diagram that shows how an ATAPI command is sent.When the decoding unit 105 outputs the ATAPI command to the secondpacket processing unit 102 b, the second packet processing unit 102 bgenerates the ATAPI command packet and sends it. The first packetprocessing unit 102 a outputs the ATAPI command of the received ATAPIcommand packet to the drive device 101.

When there is no data to be transmitted as command, the first packetprocessing unit 102 a and the second packet processing unit 102 bgenerate a NULL packet and send it.

Next, operations of each device and data flows will be explained. FIG.18 is a diagram that shows operations performed when DVD-Video data isread out from the drive device 101 and the data flows at that time.

First, using the ATAPI command packet, the decoding unit 105 notifiesthe drive device 101 of the instruction of reading out the data (dataRead) via the first packet processing unit 102 b and the first packetprocessing unit 102 a. In response to this notice, the stream data readby the drive device 101 is sent to the second packet processing unit 102b via the first packet processing unit 102 a and the transmission path104 (not shown in the figure).

Although the arrows are omitted in FIG. 18, the first packet processingunit 102 a packetizes the stream data in the packet formats as shown inFIG. 14 and FIG. 15, and the command in the packet formats as shown inFIG. 10˜FIG. 13. More specifically, the first packet processing unit 102a packetizes one sector data received from the drive device 101 into thestream data packet.

When the decoding unit 105 receives the stream data from the secondpacket processing unit 102 b and decodes the compressed data, the speedof decoding the stream data could be unable to follow the speed ofreceiving it. In that case, the decoding unit 105 instructs the secondpacket processing unit 102 b to temporarily stop data transfer from thedrive device 101.

On the other hand, the second packet processing unit 102 b, which holdsthe stream data of the stream data packet sent from the first packetprocessing unit 102 a in its internal buffer 107 b, judges whether thedata of a predetermined value (90%, for instance) or more has beenstored or not. When the second packet processing unit 102 b receives theinstruction to temporarily stop the data transfer from the decoding unit105, or it judges that the data in the buffer 107 b is the predeterminedvalue a or more (S1001), it sends a NULL packet of the command with theflow control information embedded to temporarily stop the data transfer(data Stop) to the first packet processing unit 102 a. Specifically, C1in the control data part 206 is set to be “H” (Wait).

Upon receiving the instruction of temporary stopping the data transfer,via the first packet processing unit 102 a, the drive device 101suspends the transfer of the stream data. The first packet processingunit 102 a stops packetizing the data, and outputs the NULL packet ofthe command packet without the data part and the NULL packet having nostream data to be packetized (which are not shown in FIG. 18).

After a while, when the decoding speed of the decoding unit 105 hascaught up with the speed of receiving the stream data, the decoding unit105 instructs the second packet processing unit 102 b to resume the datatransfer from the drive device 101. In response to this instruction,when the second packet processing unit 102 b judges that the stream datastored in the buffer 107 b has become a predetermined value b (10%, forinstance) or less (S1002), it instructs the first packet processing unit102 a to resume the data transfer (data Req) using the NULL packet.

Furthermore, when the decoding unit 105 wants to stop the reproductionof the stream data halfway or switch it to the reading of the data atanother address, it can instruct to clear the remaining data in thebuffer of the first packet processing unit 102 a with a signal of bufferclear indicated in the header of the command. Upon receiving theinstruction of the buffer clear with the signal of buffer clear, thefirst packet processing unit 102 a abandons all the stream data that itholds.

In the above-mentioned manner, the flow control between the decodingunit 105 and the drive device 101 is executed.

As described above, since (i) the transmission device 10 of the presentembodiment includes the sending device 11 that packetizes the streamdata and the command separately and outputs them, and (ii) the receivingdevice 12 that outputs the packet in which the command and the flowcontrol information are multiplexed, all of the stream data, the commandand the flow control information can be sent and received using thesynchronous channel area 703 of the transmission path 104. Therefore,when the transmission method of the transmission path 104 is applied tothe MOST method, the bandwidth of the transmission path 104 can use usedefficiently without using the asynchronous channel area 704.

The present embodiment is configured so as to transmit the commandpacket and the stream data packet separately, but it can be configuredto execute the flow control using the stream data packet only byincorporating the flow control information into the header 201 of thestream data packet, as shown in FIG. 14 and FIG. 15.

As mentioned above, according to the transmission method of theembodiment of the present invention, the stream data, the command andthe flow control information are all transmitted using the synchronouschannel. As a result, the effect of the data delay of flow controlinformation can be reduced, and therefore an application such asDVD-Video requiring a real-time control of data reading/writing can berealized. In addition, since the ATAPI command is transmitted,interconnection is easy.

In the above embodiment, the transmission method of the presentinvention has been explained in the case of the sending device and thereceiving device, separately, for convenience. However, by configuringthe method so that the sending device has the functions of the receivingdevice and the receiving device has the function of the sending device,it is possible to transmit the stream data, command and the flow controlinformation in each direction using the synchronous channel.

Also, in the above embodiment, a DVD-Video drive has been explained asan example of the drive device 101. However, anything that transmits thestream data and the command which must be transmitted in real time, forexample, a drive of a recording medium such as CD, MD, DAT, DVD-Audio ora hard disk, or a tuner for digital TV broadcast or a digital radio, areapplicable.

Furthermore, in the present embodiment, it has been explained that theconstruction of the drive device 101 is in accordance with the ATA orATAPI standard, but it is not limited to these standards. Therefore, theregister 108 a is not always necessary in that case. Likewise, theregister 108 b of the decoding unit 105 in the receiving device 12 isnot always necessary, too.

The decoding unit 105 can be uniquely determined if only the drivedevice 101 is determined. The decoder of MPEG-2 is described in thepresent embodiment because the drive device 101 is a DVD-Video drive,but another decoder can be used, or the decoder can be omitted. Anydecoder that fits the drive device 101 is applicable.

Also, the constructions of the first packet processing unit 102 a andthe second packet processing unit 102 b as shown in FIG. 6˜FIG. 9 arejust examples. They are not limited to these constructions, and may bearbitrary constructions that can realize same functions.

Also, the structures of the command packet as shown in FIG. 4˜FIG. 13are just examples, and an arbitrary structure is applicable if it cantransmit the ATAPI command and further multiplex the flow controlinformation. In addition, the structures of the stream data packet asshown in FIG. 14 and FIG. 15 are also examples, and an arbitrarystructure is applicable if it can transmit the stream data such asDVD-Video which is read out in response to the ATAPI command.

The present embodiment is configured so that the receiving device 12reads out the stream data from the sending device 11 using the ATAPIcommand. However, it is applicable as a method of transmitting a packetformat as it is if it is configured so that the receiving device 12writes the stream data in the sending device 11 using the ATAPI command.In this case, the display device 106 and the decoding unit 105 arereplaced with the drive device 101 and the stream data is transmitted inthe reverse direction, the flow is also controlled in the reversedirection.

In the present embodiment, the response to the command packet has notbeen described. However, if it is configured to return a response packetindicating success or failure of reception, reliability of transmissionimproves, of course.

In the present embodiment, the transmission path 104 of the MOST methodhas been explained as an example, but any digital transmission methodusing the synchronous channel area, such as the transmission methodpursuant to the IEEE1394 standard, is applicable.

Furthermore, the present embodiment is configured so as to use thesynchronous channel as a channel for transmitting the stream data.However, an asynchronous channel that does not guarantee to send datawithin a certain time period of a transmission delay may be used if itis possible to execute the flow control using the flow controlinformation.

As described above, when an enormous amount of data such as DVD-Video istransmitted, via a network, the transmission method, the sending device,and the receiving device according to the present invention are suitablefor a transmission system for which the method of transmittinginformation for flow control is not determined, although the flowcontrol is required for adjusting the transmission amount of data inreal time due to the difference of data processing capability betweenthe sending side and the receiving side.

1. A transmission device comprising: a sending device; and a receivingdevice, wherein said sending device and said receiving device areconnected to each other via a transmission path compliant with a MOSTmethod, wherein said sending device includes: a drive device that readsstream data from a disk on which the stream data is recorded, and thatoutputs the read stream data; a first packet processing unit configuredto receive the stream data from said drive device, and generate a streamdata packet using the stream data; and a first transmission path I/Funit configured to output the stream data packet generated by said firstpacket processing unit to the transmission path, wherein said receivingdevice includes: a second transmission path I/F unit configured toreceive the stream data packet via the transmission path; a secondpacket processing unit configured to extract stream data from the streamdata packet received by said second transmission path I/F unit, andgenerate a first command packet in which predetermined flow controlinformation is placed; and a decoding unit configured to decode thestream data extracted by said second packet processing unit, anddetermine whether or not it is necessary to cause said sending device tosuspend, based on a process status of the decoding, sending of thestream data, wherein said second packet processing unit is configured toplace, in a header of the first command packet, flow control informationused for causing said sending device to suspend the sending of thestream data, when said decoding unit determines that the suspension ofthe sending of the stream data is necessary, wherein said secondtransmission path I/F unit is configured to allocate, to a synchronouschannel area compliant with the MOST method, the first command packet inwhich the flow control information is placed, and output the firstcommand packet to the transmission path, wherein said drive devicedetermines a status of said drive device regarding either the reading orthe outputting of the stream data, wherein said first packet processingunit is configured to generate a second command packet by packetizing acommand including flow control information indicating the statusdetermined by said drive device, wherein said first transmission pathI/F unit is configured to output the generated second command packet tothe transmission path, wherein said first packet processing unit isconfigured to place, in a header of the second command packet, flowcontrol information indicating the status of said drive device, andwherein said first transmission path I/F unit is configured to allocate,to a synchronous channel area of a frame compliant with the MOST method,the stream data packet and the second command packet in which the flowcontrol information indicating the status of said drive device isplaced, and output the stream data packet and the second command packet.2. The transmission device according to claim 1, wherein said firsttransmission path I/F unit is configured to receive the first commandpacket via the transmission path, wherein said first packet processingunit is configured to extract the flow control information from theheader of the received first command packet, and output the extractedflow control information to said drive device, and wherein said drivedevice receives the flow control information from said first packetprocessing unit, and suspends, based on the flow control information,the outputting of the stream data by said drive device.
 3. Thetransmission device according to claim 1, wherein the first commandpacket and the second command packet each include (i) the header furtherincluding information indicating a synchronization code and a packettype, and (ii) a data part.
 4. The transmission device according toclaim 1, wherein said sending device includes a multiplexing unitconfigured to multiplex the stream data packet and the second commandpacket into a multiplexed packet, and wherein said first transmissionpath I/F unit is configured to output the multiplexed packets to thetransmission path.
 5. The transmission device according to claim 1,wherein said drive device is a DVD device, wherein said decoding unit isconfigured to decode stream data compressed based on an MPEG-2 standard,and wherein said first transmission path I/F unit is configured toallocate a bandwidth of at least 11.08 Mbps to the stream data packetand output the stream data packet, so as to transmit the stream datapacket on the transmission path.
 6. A transmission device comprising: asending device; and a receiving device, wherein said sending device andsaid receiving device are connected to each other via a transmissionpath, wherein said sending device includes: a DVD device that readsstream data compressed in compliance with an MPEG-2 standard from a DVDon which the stream data is recorded, and that outputs the read streamdata; a first packet processing unit configured to receive the streamdata from said DVD device, and generate a stream data packet using thestream data; and a first transmission path I/F unit configured toallocate a bandwidth of at least 11.08 Mbps to the stream data packetgenerated by said first packet processing unit, and output the streamdata packet generated by said first packet processing unit to thetransmission path, so as to transmit the stream data packet on thetransmission path, wherein said receiving device includes: a secondtransmission path I/F unit configured to receive the stream data packetvia the transmission path; a second packet processing unit configured toextract stream data from the stream data packet received by said secondtransmission path I/F unit, and generate a first command packet whichallows setting of predetermined flow control information; and a decodingunit configured to decode the stream data extracted by said secondpacket processing unit, and determine whether or not it is necessary tocause said sending device to suspend, based on a process status of thedecoding, sending of the stream data, wherein said second packetprocessing unit is configured to place, in a header of the first commandpacket, flow control information used for causing said sending device tosuspend the sending of the stream data, when said decoding unitdetermines that the suspension of the sending of the stream data isnecessary, wherein said second transmission path I/F unit is configuredto allocate, to a channel area where transmission of information withina certain time period of a transmission delay is guaranteed, the firstcommand packet in which the flow control information is placed, andoutput the first command packet to the transmission path, wherein saidDVD device determines a status of said DVD device regarding either thereading or the outputting of the stream data, wherein said first packetprocessing unit is configured to generate a second command packet bypacketizing a command including flow control information indicating thestatus determined by said DVD device, wherein said first transmissionpath I/F unit is configured to output the generated second commandpacket to the transmission path, wherein said first packet processingunit is configured to place, in a header of the second command packet,control signal information indicating the status determined by said DVDdevice, and wherein said first transmission path I/F unit is configuredto allocate, to a channel area where transmission of information withina certain time period of a transmission delay is guaranteed, the streamdata packet and the second command packet, and output the stream datapacket and the second command packet.
 7. The transmission deviceaccording to claim 6, wherein said first transmission path I/F unit isconfigured to receive the first command packet via the transmissionpath, wherein said first packet processing unit is configured to extractthe flow control information from the header of the received firstcommand packet, and output the extracted flow control information tosaid DVD device, and wherein said DVD device receives the flow controlinformation from said first packet processing unit, and suspends, basedon the flow control information, the outputting of the stream data bysaid DVD device.
 8. The transmission device according to claim 6,wherein said sending device includes a multiplexing unit configured tomultiplex the stream data packet and the second command packet into amultiplexed packet, and wherein said first transmission path I/F unit isconfigured to output the multiplexed packets to the transmission path.9. The transmission device according to claim 6, wherein the firstcommand packet and the second command packet each include (i) the headerfurther including information indicating a synchronization code and apacket type, and (ii) a data part.
 10. The transmission device accordingto claim 6, wherein the transmission path is a transmission pathcompliant with a MOST method, wherein said second transmission path I/Funit is configured to allocate, to a synchronous channel area of a framecompliant with the MOST method, the first command packet, and output thefirst command packet on the transmission path, and wherein said firsttransmission path I/F unit is configured to allocate, to the synchronouschannel area of the frame compliant with the MOST method, the streamdata packet and the second command packet, and output the stream datapacket and the second command packet on the transmission path.
 11. Asending device in a transmission device including said sending deviceand a receiving device that are connected to each other via atransmission path compliant with a MOST method, said sending devicecomprising: a drive device that reads stream data from a disk on whichthe stream data is recorded, and that outputs the read stream data; afirst packet processing unit configured to receive the stream data fromsaid drive device, and generate a stream data packet using the streamdata; and a first transmission path I/F unit configured to output thestream data packet generated by said first packet processing unit to thetransmission path, wherein said first transmission path I/F unit isconfigured to receive, via the transmission path, a first command packetthat is outputted from the receiving device, wherein said first packetprocessing unit is configured to extract flow control information from aheader of the received first command packet, and output the extractedflow control information to said drive device, wherein said drive devicereceives the flow control information from said first packet processingunit, and suspends, based on the flow control information, theoutputting of the stream data by said drive device, wherein said drivedevice determines a status of said drive device regarding either thereading or the outputting of the stream data, wherein said first packetprocessing unit is configured to generate a second command packet bypacketizing a command including flow control information indicating thestatus determined by said drive device, wherein said first transmissionpath I/F unit is configured to output the generated second commandpacket to the transmission path, wherein said first packet processingunit is configured to place, in a header of the second command packet,flow control information indicating the status of said drive device, andwherein said first transmission path I/F unit is configured to allocate,to a synchronous channel area of a frame compliant with the MOST method,the stream data packet and the second command packet in which the flowcontrol information indicating the status of said drive device isplaced, and output the stream data packet and the second command packet.12. A sending device in a transmission device including said sendingdevice and a receiving device that are connected to teach other via atransmission path, said sending device comprising: a DVD device thatreads stream data compressed in compliance with an MPEG-2 standard froma DVD on which the stream data is recorded, and that outputs the readstream data; a first packet processing unit configured to receive thestream data from said DVD device, and generate a stream data packetusing the stream data; and a first transmission path I/F unit configuredto allocate a bandwidth of at least 11.08 Mbps to the stream data packetgenerated by said first packet processing unit, and output the streamdata packet to the transmission path, so as to transmit the stream datapacket on the transmission path, wherein said first transmission pathI/F unit is configured to receive, via the transmission path, a firstcommand packet that is outputted from the receiving device, wherein saidfirst packet processing unit is configured to extract the flow controlinformation from a header of the received first command packet, andoutput the extracted flow control information to said DVD device,wherein said DVD device receives the flow control information from saidfirst packet processing unit, and suspends, based on the flow controlinformation, the outputting of the stream data by said DVD device,wherein said DVD device determines a status of said DVD device regardingeither the reading or the outputting of the stream data, wherein saidfirst packet processing unit is configured to generate a second commandpacket by packetizing a command including flow control informationindicating the status determined by said DVD device, wherein said firsttransmission path I/F unit is configured to output the generated secondcommand packet to the transmission path, wherein said first packetprocessing unit is configured to place, in a header of the secondcommand packet, control signal information indicating the statusdetermined by said DVD device, and wherein said first transmission pathI/F unit is configured to allocate, to a channel area where transmissionof information within a certain time period of a transmission delay isguaranteed, the stream data packet and the second command packet, andoutput the stream data packet and the second command packet.
 13. Atransmission method for use in a transmission device including a sendingdevice and a receiving device that are connected to each other via atransmission path compliant with a MOST method, wherein saidtransmission method for use in the sending device comprises: readingstream data from a disk on which the stream data is recorded, andoutputting the read stream data; generating a stream data packet usingthe stream data outputted in said outputting of the read stream data;and outputting the stream data packet generated in said generating tothe transmission path, wherein said transmission method for use in thereceiving device comprises: obtaining the stream data packet via thetransmission path; extracting stream data from the stream data packetobtained in said obtaining, and generating a first command packet inwhich predetermined flow control information is placed; and decoding thestream data extracted in said extracting, and determining whether or notit is necessary to cause the sending device to suspend, based on aprocess status of said decoding, sending of the stream data, wherein, insaid extracting and generating, flow control information used forcausing the sending device to suspend the sending of the stream data isplaced in a header of the first command packet, when it is determined insaid decoding and determining that the suspension of the sending of thestream data is necessary, wherein, in said obtaining, the first commandpacket, in which the flow control information is placed, is allocated toa synchronous channel area compliant with the MOST method, and isoutputted to the transmission path, and wherein said transmission methodfor use in the sending device further comprises: determining a status ofa drive device, which performs said reading of the stream data from thedisk, regarding either the reading or the outputting of the stream data;generating a second command packet by packetizing a command includingflow control information indicating the status determined by saiddetermining of the status of the drive device; outputting the generatedsecond command packet to the transmission path; placing, in a header ofthe second command packet, flow control information indicating thestatus determined by said determining of the status of the drive device;and allocating, to a synchronous channel area of a frame compliant withthe MOST method, the stream data packet and the second command packet inwhich the flow control information indicating the status determined bysaid determining of the status of the drive device is placed, andoutputting the stream data packet and the second command packet.
 14. Atransmission method for use in a transmission device including a sendingdevice and a receiving device that are connected to each other via atransmission path, wherein said transmission method for use in thesending device comprises: reading stream data compressed in compliancewith an MPEG-2 standard from a DVD on which the stream data is recorded,and outputting the read stream data; generating a stream data packetusing the stream data outputted in said outputting of the read streamdata; and allocating a bandwidth of at least 11.08 Mbps to the streamdata packet generated in said generating, and outputting the stream datapacket generated in said generating to the transmission path, so as totransmit the stream data packet on the transmission path, wherein saidtransmission method for use in the receiving device comprises: obtainingthe stream data packet via the transmission path; extracting stream datafrom the stream data packet obtained in said obtaining, and generating afirst command packet in which predetermined flow control information isplaced; and decoding the stream data extracted in said extracting, anddetermining whether or not it is necessary to cause the sending deviceto suspend, based on a process status of said decoding, sending of thestream data, wherein, in said extracting and generating, flow controlinformation used for causing the sending device to suspend the sendingof the stream data is placed in a header of the first command packet,when it is determined in said decoding and determining that thesuspension of the sending of the stream data is necessary, wherein, insaid obtaining, the first command packet in which the flow controlinformation is placed, is allocated to a channel area where transmissionof information within a certain time period of a transmission delay isguaranteed, and is outputted to the transmission path, and wherein saidtransmission method for use in the sending device further comprises:determining a status of a DVD device, which performs said reading of thestream data, regarding either the reading or the outputting of thestream data; generating a second command packet by packetizing a commandincluding flow control information indicating the status determined bysaid determining of the status of the DVD device; outputting thegenerated second command packet to the transmission path; placing, in aheader of the second command packet, control signal informationindicating the status determined by said determining of the status ofthe DVD device; and allocating, to a channel area where transmission ofinformation within a certain time period of a transmission delay isguaranteed, the stream data packet and the second command packet, andoutputting the stream data packet and the second command packet.
 15. Acomputer-readable recording medium having a program recorded thereon,the program for use in a sending device in a transmission deviceincluding the sending device and a receiving device that are connectedto each other via a transmission path compliant with a MOST method, saidprogram causing a computer to execute a method comprising: readingstream data from a disk on which the stream data is recorded, andoutputting the read stream data; generating a stream data packet usingthe stream data outputted in said outputting of the read stream data;and outputting the stream data packet generated in said generating tothe transmission path, wherein, in said outputting of the stream datapacket, a first command packet that is outputted from the receivingdevice is received via the transmission path, wherein, in saidgenerating, flow control information is extracted from a header of thereceived first command packet, wherein, in said reading and outputting,the outputting of the stream data is suspended based on the flow controlinformation extracted in said generating, and wherein the methodexecuted by the computer further comprises: determining a status of adrive device, which performs said reading of the stream data from thedisk, regarding either the reading or the outputting of the stream data;generating a second command packet by packetizing a command includingflow control information indicating the status determined by saiddetermining of the status of the drive device; outputting the generatedsecond command packet to the transmission path; placing, in a header ofthe second command packet, flow control information indicating thestatus determined by said determining of the status of the drive device;and allocating, to a synchronous channel area of a frame compliant withthe MOST method, the stream data packet and the second command packet inwhich the flow control information indicating the status determined bysaid determining of the status of the drive device is placed, andoutputting the stream data packet and the second command packet.
 16. Acomputer-readable recording medium having a program recorded thereon,the program for use in a sending device in a transmission deviceincluding the sending device and a receiving device that are connectedto each other via a transmission path, said program causing a computerto execute a method comprising: reading stream data compressed incompliance with an MPEG-2 standard from a DVD on which the stream datais recorded, and outputting the read stream data; generating a streamdata packet using the stream data outputted in said outputting of theread stream data; and allocating a bandwidth of at least 11.08 Mbps tothe stream data packet generated in said generating, and outputting thestream data packet generated in said generating to the transmissionpath, so as to transmit the stream data packet on the transmission path,wherein, in said allocating and outputting, a first command packet thatis outputted from the receiving device is received via the transmissionpath, wherein, in said generating, flow control information is extractedfrom a header of the received first command packet, wherein, in saidreading and outputting, the outputting of the stream data is suspendedbased on the flow control information extracted in said generating, andwherein the method executed by the computer further comprises:determining a status of a DVD device, which performs said reading of thestream data, regarding either the reading or the outputting of thestream data; generating a second command packet by packetizing a commandincluding flow control information indicating the status determined bysaid determining of the status of the DVD device; outputting thegenerated second command packet to the transmission path; placing, in aheader of the second command packet, control signal informationindicating the status determined by said determining of the status ofthe DVD device; and allocating, to a channel area where transmission ofinformation within a certain time period of a transmission delay isguaranteed, the stream data packet and the second command packet, andoutputting the stream data packet and the second command packet.